Device for bending tubes



March 21, 1961 A. HUET DEVICE EOE BENDING TUBES Filed June 21, 1957 INVENTOR. ANDRE HUET WM@ ATTORNEY 2,975,820 DEVICE non nnNnnvG runas Andr Huet, 4S Ave. du President Wilson, Paris, France 'Filed 'June 21, 1957, Ser. No. 667,238

Claims priority, application France July 3, 1956 V7 claims. (Cl. 153-48) There are known methods for bending tubes, wherein by means of a punch pressure is exerted on the tube which, atrthe end of the operation, is thereby pressed into aA suitably shaped die. It has also been proposed to produce prior to and in the course of the pressingY operation a dierence in temperature between that area of the tube which ultimately becomes the inside bend of the elbow and which should be hotter, and the outside bend which is kept cooler. This temperature gradient facilitates the bending of the metal and diminishes or suppresses the thinning of the wall in the outside bend of the elbow.

In hisprevious application No. 591,132 of June 13, 1956, now Patent No. 2,897,872 relating to improvements in or relating to methods and apparatus for bending tubes, applicant has proposed that in such a method the cooling of the outside bendrof the elbow should be performed byl atomisation of aV liquid coolant inside the tube which tube is preferably filledV with sand. i

YApplicant has observed that said tube bending method can be performed without using a die when the temperature gradient of the tube is strictly maintained and when the punch used is suiiiciently wide. To be precise-the width of the punch may be such as to offer a support for the whole length of the tube to be bent; the punch has a groove of substantially semicircular cross-section equal to that of the tube and a bulge in the area vicinal to the central generatrix of the inside bend of the elbow so that the bottom of the punch does not at first come into contact with the heated tube surface. Moreover, the punch has cheeks extending substantially beyond the half-section of the tube so as to prevent any lateral bulging out of the latter during the bending operation.

When such a punch is used, the die can be dispensed with; the bending of the tube, for which a suitable temperature gradient is provided and which need not be filled with sand for the purpose, is correctly performed by the pressure of the punch alone, which pressure is applied to the cold tube areas on either side of the heated tube area.

Alternatively, the present invention proposes a method according to which, in the course of a subsequent operation, the outside bend of the elbow can be shaped with the use of a suitable die, in which case the outside bend is made hotter than the inside bend which may optionally even be cooled.

To facilitate the removal of the tube compressed by the punch, or worked in the die, there are provided inside the punch or inside the die and in any desired central point and/or at the extremities, one or several sliding members acting as ejectors which possess a certain lateral mobility by virtue of the provision of a suitable device to enable the tube to be wrenched away from the punch or the die on completion of the operation.

The following description, with reference to the accompanying drawing, illustrates the performance of the present invention.

Fig. 1 is a horizontal section through the punch and the tube prior to the bending operation;

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Fig. 2 is a view similar to that of Fig. 1, after the tube has been bent;

Fig. 3 is a section on lII--Ill of IFig.' 2;

Fig. 4 is a section, along the axis of the elbow, of an ejector die for die-shaping the outside bend of the elbow.

As will be seen from Fig. 1, the tube zito be bent is pressed against two forming rollers b, c, there being no need for the provision of a die for shaping the outside bend of the elbow. The punch d, which exerts its pressure in the direction of the arrow F, bends the tube and (as shown in Fig. 2) sufficiently wide to support the whole area of the ultimate elbow. As shown in Fig. 3, this punch has a groove of substantially semicircular crosssection, which bulges out at e, and incorporates cheeks f1, f2 which are sufficiently high as to prevent any lateral bulging out of the tube. As has been said, the tube must be heated to a higher temperature in the area A (shown cross-hatched in Fig. 1) which will ultimately be the inside bend of the elbow. The heating is performed, for example, before the tube is inserted Yin the bending device in a manner such that the outside bend of the elbow is kept relatively cold by means of an atomised liquid coolant--such as water or strongly humidied air--by means of a tube g inserted into the tube a (which need not be lled with sand). It is important that the temperature gradient should be maintained during the bending operation, and to ensure this a partitioning strip of sheet metal l1 is inserted in the tube to divide the inside of the tubeV into two compartments: One compartment faces the area to be heated A, whereas the other faces the tube area which is toremain cold, and in this latter compartment the tube g atornises the liquid coolant. The partition h and the tube g can be integral and hinged at i and j (see Fig.'2) so as to bend and follow the nal shape of the elbow'.

To keep the area A of the tube hotY during the bending operation there is provided inside the tube a a arne tube in the area A, or, alternatively, as shown in the drawing, a bore k can be provided in the punch h through which a flame tube I can be introduced so that its ilames can heat the area A of the tube by virtue of the communication between the bore k and the bulging bottom e of the groove in the punch.

On completion of the bending operation the bore k can be used to inject a liquid coolant into the'punch so as to cool it. l

It will be realised that at the start of the bending operation the inside faces of the cheeks f1, f2 of the punch rest against the area C, D (Fig. 3) of the tube which are located in the cold zone of the tube, since the partitioning member h has the shape of a V (see Fig. 3). Accordingly, the initial pressure of the punch acts on less deformable parts of the tube whereby the regularity of the cross-section of the elbow is maintained. The bulge e in the bottom of the groove in the punch accepts the thickened portion t of the wall as shown in Fig. 2-which is formed on the inside bend of the elbow during the bending operation.

On completion of the operation, when the tube has been bent and is positioned as shown in Pig. 3, it may be difficult to withdraw it from the punch d. To facilitate such withdrawal there is provided inside the punch d an ejection device m comprising a mobile portion inside the punch d which portion, with the aid of the ram n (shown diagrammatically), can slide in the direction of the arrow B by the distance o which is a. gap left between the ejector m and the cheeks of the punch (Fig. 3). The ejector m may consist of several segments acting at the centre and/ or at the extremities.

In general, the tube is bent with the punch alone in perfectly satisfactory fashion, but according to the present Patented Mar. 21, A1961y invention it is also possible to shape the outside bend of the elbow in the course of a second operation.

This is performed with a device shaped opposite to that described above. The heated area of the tube is that which ultimately becomes the outside bend of the elbow, whereas the inside bend of the elbow is preferably kept at a -relatively low temperature. A die p, having the shape of the outside bend of the finished elbow, is shown in section in Fig. 4; it has a groove q whose semicircular cross-section is equal to that of the tube. Said die is pressed against the outside bend of the elbow and thus shapes it. Also in this case the die p comprises an ejector r which, when pushed by the ram s, can slide a certain distance in the direction of the arrow C whereby the tube a is ejected from the die p'.

The illustrations represent the bending of a 90 tube elbow, but the tube can of course be bent through any angle smaller or greater than 90 by decreasing or increasing the stroke of the punch d. l

What I claim is:

1. A device for bending a tube under the action of a punch adapted to exert pressure on the tube, while maintaining the tube at a suitable temperature gradient, comprising, in combination, a partitioning member insertable in longitudinally-disposed position interiorly of the empty tube to be bent, said partitioning member dividing the interior of said tube into two compartments, one of said compartments including the portion of the tube corresponding to the outside of the bend to be formed and the other of said compartments including the portion of the tube corresponding to the inside of the bend to be formed, means for cooling said rst-named compartment, a punch adapted to exert a pressure on the tube having a length suii'icient to overlie the bent portion of the tube to be bent, a roller on eachside of the punch to support the straight tube, a groove formed in the punch and having a bulge at its bottom and two lateral cheeks of such height that, at the beginning of the bending operation, said cheeks engage that area of the tube which is maintained at a lower temperature.

2. A device according to claim 1, wherein the partitioning member has la V-shaped cross-section and is arranged inside the tube so that the lateral walls of the tube which come into contact with the punch cheeks during the bending operation are located at the level of the first-named compartment which is kept cold.

3. A device according to claim 1, wherein said means for cooling comprises a cooling tube connected with the partitioning member and adapted for atomizing a liquid coolant inside the tube to be bent.

4. A device according to claim 1, wherein a bore is provided in the punch under the groove adapted to receive the -tube to be bent, and means inside said bore to receive a heating medium.

5. A device according to claim 1, wherein the partitioning member adapted to be inserted in the tube is made of hinged segments.

6. VA device according to claim' 1, comprising, inside the punch, ejector means to facilitate the removal of the tube from the punch on completion of the bending operation.

7. A device according to claim 6, wherein said ejector means is deiined by the portion of the punch in which is formed the groove to receive the tube during the bending operation, said portion being movable and being adapted to slide in the remainder of the punch.

References Cited in the le of this patent UNITED STATES PATENTS Linden et al. Dec. 23, 1947 

